62 
NATURE 
If we look just now in the Botanic Garden at any of the 
old summer beds of half-hardy plants, we shall see them 
shrouded in a maze and network of white fleecy mould, 
That mould is a fungus finishing the work of extermination 
which the frost has begun, and then burning the bodies. In 
all the odd corners there are heaps of rotting vegetation. 
These stems and leaves are not rotting of themselves ; 
heat them to 212° F., so as to kill the seeds of the fungi, 
and seal them up in closed cases, and although they will 
slowly decompose, they will never rot. They are being 
burned by the process of respiration of fungi just as effec- 
tually as they would be if they were collected into a 
heap, dried, and set fire to. Most of these fungi are very 
minute, but each of them, when it is found in anything 
like a well-developed condition, is thoroughly characte- 
ristic. Still they are so small and so simple that it is 
difficult to distinguish parts of those organs whose form 
is not strongly marked. 
I will give a brief sketch of the life-histories of one 
or two of these fungi, and the first I will choose is a well- 
known mildew, JZucor stolonifer. This species is often 
found on juicy fruits, covering them with white woolly 
patches scattered over with small black heads, and pro- 
ducing a very rapid putrefaction beneath the surface of 
the fruit. A number of delicate branching filaments form a 
rich network in the substance of the fruit, filaments which 
are easily distinguished from those of some nearly-allied 
forms by their long simple tubes without partitions. These 
delicate filamentous tubes, which are the parts first to ap- 
pear, and form the basis, as it were, of the fungus, are called 
the mycelium, and are found in almost all fungi. From 
the mycelium, at certain points, long rather wide tubes 
start from the surface on which the fungus is growing 
obliquely into the air, and, after running along for a time, 
again dip down and give origin to other tufts of my- 
celium tube-roots, At the point where these roots come 
off, as at the bud of a strawberry-runner, a little tuft of 
tubular stems rises upvertically,and ends in roundvesicles 
which at first are entirely filled with transparent proto- 
plasm. These are cut off from the stem by a partition 
which is at first flat, but afterwards assumes an arched 
form, giving the space between it and the outer wall the 
shape of a very deep meniscus. The protoplasm in the 
space ultimately breaks up into a mass of black polygonal 
spores, which escape by the giving way of the outer wall of 
the sporangium. These spores are thus produced by no 
process of true reproduction, but are simply separated 
particles of the protoplasm of the parent plant. In hot 
summer weather, chiefly on the surface of sour fruit, 
Mucor stolonifer forms thick patches, with broad stolons, 
and from these, twigs spread over the surface of the 
fruit. When two of these twigs meet one another they 
form large vesicular expansions, and then apply themselves 
to one another. A diaphragm is formed across each of 
the vesicles, thus cutting off the distal end of the vesicle, 
which is filled with protoplasm. The double wall be- 
tween the two cells gives way, and the protoplasm in the 
two unites, as in the union of the cell-contents in the con- 
jugation of Zyguema. These “coupling cells” have thus 
become fused into a single cell called a zygospore, which 
goes on enlarging, and is covered with a thick skin, 
The simple spores, when scattered on moist ground, 
send out filamentous shoots of mycelium, which in their 
| in a solution in which it is fairly nourished without a — 
turn originate stolons as before ; but the zygospores do not — 
produce mycelial filaments when they germinate, but form 
one or two sporangium-bearers directly at{the expense — 
of the substance of the zygospore, and the ordinary course — 
of growth is resumed from their spores. There are thus two — 
modes of multiplication in JZ7ucorv—one by sporangia and 
spores, non-sexual, a simple method of propagation by 
buds—the other a true reproductive process, by the con-— 
jugation of male and female elements. It seems to be — 
only occasionally and under specially favourable circum-— 
stances that the latter process occurs, and this mildew — 
often goes on reproducing itself by spores alone for many 
generations. 
The life history of JZucor mucedo, one of the com- 
monest of the mildews, is not yet thoroughly known. — 
Here the cells are again simple and undivided, but each 
sporangium-bearer usually ends in several large sporangia. 
Under certain circumstances this sporangium-bearer — 
sends out tufts of finely dividing twigs, each of which — 
ends in a small sporangium, which, to distinguish it 
from the larger form, has been called a sporangiolum, 
At other times processes are produced from the main cells 
which rise into delicate tubular branches, and give off 
globular cells which are called conédia—simple external 
spores, differing entirely in their character from the spores — 
produced in sporangia; and if this mould be grown ~ 
full supply of oxygen gas, long fibres are produced 
which break up into a multitude of separate bead-like 
cells filled with protoplasm, and capable of reproducing 
the organism, WYVILLE THOMSON 
(To be continued.) 
EXPLORATION OF THE SOUTH POLAR 
REGIONS 
Il. 
HILE Balleny was making the discoveries to which 
\ we alluded at the close of the previous article, two 
other expeditions were actively pursuing their researches 
and extending our knowledge of the Antarctic regions, — 
a French expedition under Dumont d’Urville and an 
American under Lieutenant Wilkes. Neither expedition 
was originally intended for South Polar exploration, and — 
to this among other reasons is it to be ascribed that the 
results, with respect to the exploration of the South Polar 
regions, are of but little value compared with those ob-— 
tained by the almost contemporaneous English expedition, 
From the South Shetlands D’Urville directed his course 
to the south, and discovered on February 27, 1838, in 63° 
10’ S, lat. and 57° 5’ W. long., a coast which bears the 
name of Louis Philippe Land, and rises to a height of 
between 2,000 and 3,000 feet above the sea, The general 
outlines of this coast were already indicated on Weddell’s 
chart. 1K: 
Two years later we find the same explorer again active, 
and with a better result, In January 1840 he left Tas- 
mania for the south, steering for the region between 120° 
and 160° E. long, On January 19, in 66° S, lat., he 
found land from 2,000 to 3,000 ft. high, entirely covered 
with snow and ice, On the 21st some of the sailors landed 
on a little island consisting of gneiss, which D’Urville 
named Adelie Land. On the 30th and 31st D’Urville sailed 
